The intellectual landscape of Yemen significantly changed during the sixth/twelfth century, when the region raised as a new centre of Mu'tazilite teaching. This development took place in a vibrant intellectual environment and was marked by debates with other local religious strands, including the Mutarrifiyya, Isma'ilis or followers of the Ash'arite school of theology. One of the most important representatives of the new Zaydi-Mu'tazilite strand in Yemen was al-Hasan al-Rassas (d. 584/1188), whose teaching has been studied recently in considerable detail. One of the most striking features of his teaching was the emphasis he gave to discussions of metaphysical issues, including the theory of atomism, the ontology of the properties of beings or causality.
Such "philosophical inquiries" remained of central concern to the generations of theologians that immediately followed al-Rassas's death. A striking example is Humayd b. Ahmad al-Muhalli, (d. 652/1254), who attempted in his al-Kawakib al-durriyya fi tafsil al-nafahat al-miskiyya to offer a comprehensive compendium of metaphysical problems. My presentation will discuss this and other Yemeni Zaydi works in metaphysics from the seventh/thirteenth century that remain in manuscript form and await to be studied in greater detail.